This invention relates to an electromagnetic shield-type doorway for buildings in which an entire building is provided with an electromagnetic shielding structure, which doorway is well-suited for application to an information network system utilizing electric waves. The invention also relates to an electromagnetic shielding system for such a doorway.
In many modern buildings, information generally is communicated between the interior and the outside of the building by making joint use of information communicating equipment such as multiple electronic exchanges and computers. With the increasing value of information, diversification of user needs with regard to information and increasingly individual nature thereof, how to transmit accurate information rapidly where large-scale buildings are involved has become of prime importance. In an effort to satisfy this need, data highway-type information networks utilizing optical fiber cables or coaxial cables have been studied and proposed.
However, with a data highway system utilizing optical fiber cables or coaxial cables, the cables must be stretched throughout all parts of the building. Extra time is needed to complete the work and additional expenses are required to lay these cables.
If electric waves are used to transmit information within the building, laying cables is unnecessary but radio law limits the usable frequency to no more than 3 T(tera) Hz owing to the emission of electrical noise waves from such a building. Another problem is that the communication system may malfunction due to electric waves from outside the building, television intermediate frequencies from inside the building, electric waves from wireless microphones, and the like.
Accordingly, in a building of the above type, the overall building is electromagnetically shielded, even at window openings and doorways, by using glass containing a mesh or glass to which an electrically conductive film has been affixed.
Merely providing the door at a doorway with an electromagnetic shielding structure does not make it possible to maintain a perfect electromagnetic shielding effect at all times since the door is opened whenever someone enters or leaves the building. At such times electric waves leak in from the doorway and impair those communications within the building that rely upon electric waves. Therefore, in a building the overall structure of which is electromagnetically shielded, it is essential that the shielding effect be maintained constantly even when a door is opened and closed.
In a case where a doorway employs a revolving door, providing the revolving door with an electromagnetic shielding property is an effective way to maintain a constant shield since the interior and exterior of the building are never opened to each other regardless of the angular position of the revolving door. However, in order to obtain smooth rotation in a conventional revolving door, a gap is provided along one longitudinal side edge and the lower edge of the door. As a result, electric waves leak through the gap whenever the revolving door is used. Thus, a satisfactory electromagnetic shield cannot be maintained at all times.
Though it has been contemplated to provide double automatic doors in order to solve the above problems, there are instances where both doors open simultaneously, as when one individual is entering while another is leaving at the same time. In such instances the integrity of the electromatic shield is not maintained.